Smoking and Ratings of Perceived Health Status
- Presenter:
Mon June 5, 2006 9:30-10:45 Room Alumni Lounge
Introduction: The perceived health status of smokers has been shown to be lower than that of nonsmokers; however, causality is not clear. Smoking could lower someone’s self-rated health status physically, due to the adverse effects of smoking; psychologically, due to feelings of guilt or of weaker self control; or due to other factors. An external factor that could increase the propensity to smoke may also cause other health-related issues, lowering perceived health status. The biochemical effect of nicotine on the nicotinic receptors in the brain suggests that smoking can also be a form of self-medication. The causative agent, which evokes the need to self-medicate, could also lead to a lower health status.
Purpose: The purpose of this study is to examine the extent to which reported quality of life differs between smokers and nonsmokers when other physical and mental health status factors are controlled for.
Methods: Data from the 2002 Medical Expenditure Panel Survey (MEPS) was used in this analysis. The dataset represented a population of 97,221,295 non-institutionalized adults in the US, 22% of which were current smokers.
To address confounding of explanatory variables by smoking, logistic regressions were run using smoking status as the dependent variable. Explanatory variables included demographics, smoking-unrelated diseases, smoking-related diagnoses, and mental/emotional characteristics. Variables that were significantly associated with smoking and smoking status were used as the explanatory variables in a linear regression with perceived health status as the dependent variable.
Results: Even after adjusting for the other significant measures of emotional and physical health, smoking remained a significant factor affecting perceived health status, although the influence of smoking on health status decreased by more than half. In the univariate model, the coefficient on smoking was 0.40. When other explanatory variables were included in the model, the coefficient on smoking status was 0.18.
The only smoking-related diagnosis significantly associated with smoking in the logistic regressions was emphysema. In the linear regression, the three factors with the largest effects on health status were perceived mental health status (0.50), diabetes (0.46), and emphysema (0.46). Mental health status also has a much larger t-value than any others do in the model; it is likely that the health and mental health status measures are correlated strongly enough that a multivariate model should be used instead with mental health status included as a dependent variable.
Discussion: A limitation of this model is the accuracy of the outcome variable, which is measured on a five-point scale, from 1 (“excellent”) to 5 (“poor”). Although this scale is treated as an interval scale, it is unlikely that ratios between adjacent values are the same throughout the scale. (The difference between “excellent” and “very good” is likely not as large as between “fair” and “poor.”) It is therefore harder to determine the exact effects on health status of a change in the explanatory variables (i.e., the coefficients are harder to interpret); however, inferences can be drawn about the relative effects of each factor in comparison with others.
